A simple and stable dual-emission fluorescent system based on R6G/Eu-MOF for the rapid and sensitive determination of orientin

A stable dual-emission fluorescent system, R6G/Eu-MOF, was obtained by simple mixing Eu-MOF with fluorescent rhodamine 6G (R6G). This system not only achieved robust dual luminescence performance at 430 nm (Eu-MOF) and 555 nm (R6G) under single-wavelength excitation, but also endowed it with significantly improved fluorescence stability. Orientin (OT), a bioactive traditional Chinese medicine (TCM) component, was found to efficiently quench the dual fluorescent emissions <i>via</i> the synergistic effect of dynamic quenching, photo-induced electron transfer and molecular interactions. Therefore, a rapid fluorescent assay for OT was developed based on the variations in fluorescence signals at 430 nm and 555 nm, as well as the alterations in the ratio between these two signals. This method can achieve highly sensitive determination of OT in the linear range of 1.1-220 μM, with a LOD of 0.26 μM at 430 nm and 0.16 μM at 555 nm (3<i>σ</i>/<i>N</i>). The R6G/Eu-MOF hybrid exhibits significantly lower detection limits and a broader linear range for OT than either R6G or Eu-MOF alone. This work presents a simple strategy to improve the water stability of Eu-MOF and also provides a rapid analysis of small molecule drugs using a fluorescence approach based on a dual-emission MOF hybrid system.